1. Field of the Invention
This invention relates to liquid-jetting heads and more particularly to liquid-jetting heads suited for producing droplets of recording liquid (ink) in ink-jet recording systems.
2. Description of the Prior Art
The ink-jet recording system is a method for recording by ejecting a recording liquid called "ink" through fine nozzles, while transforming the liquid into droplets in various ways (e.g. by application of electrostatic attraction, utilization of oscillation of piezo elements, and so on), and causing the droplets to adhere onto recording paper or the like. Liquid-jetting heads used in this system are generally provided with fine-jetting nozzles (orifices), liquid passages, and liquid-jetting energy generators, such as piezo elements or heating elements, which are set up in the ihdividual liquid-passages and generate the droplet-forming energy to exert the liquid. As in the fields of other recording systems, research and development has been made, in the field of ink-jet recording systems, for the purpose of realizing multicolor or full-color recording in addition to monochromatic recording. Liquid-jetting heads for multicolor or full-color recording need each to have a plurality of separated liquid passages and orifices for each color liquid in order to separately introduce and eject different color inks. Heretofore, however, satisfaction of the above requirements was accompanied by such difficulties that the inner structure of the heads became extremely complicated and reliable heads are hence difficult to obtain and that the heads, becoming large in size, are hardly adaptable in particular for the so-called serial recording, which performs recording with moving heads. Additionally, in order to accomplish high-speed and high-resolution recording, it is necessary for multicolor or full-color ink-jet recording heads each to have plural orifices, liquid passages, and liquid-jetting energy generators (liquid-jetting pressure generators) arranged all in much higher density. The prior art recording heads multiplied in components and integrated in a high density have drawbacks such as insufficient refilling of ink into the heads, infeasibility to accomplish real high-speed recording, and incapability of attaining high responsiveness to signals.
Another important subject imposed on liquid-jetting heads is to densify ink dots on recording paper for the purpose of improving the quality of letters printed (continuous dots are preferred in quality). However, according to the prior art, it has been very difficult on account of restrictions upon the fabrication technique to obtain such heads that give high-density ink dots.